1. Field of the Invention
Generally, the present disclosure relates to the manufacturing of sophisticated semiconductor devices, and, more specifically, to various methods of forming metal nitride layers on various types of semiconductor devices.
2. Description of the Related Art
In manufacturing semiconductor devices, it is very common to use metal nitride films or layers for a variety of purposes. For example, titanium nitride has been employed as a hard mask material that is formed above one or more layers of insulating material on an integrated circuit product. Metal nitride layers have also been employed in other applications, such as for capacitor electrodes, contacts, barrier liners, etc. Metal nitride layers may be formed by performing a chemical-based process, like a chemical vapor deposition (CVD) process using appropriate precursors, or by performing a sputtering type process, such as a physical vapor deposition (PVD) process in which material is sputtered off of an appropriate metal target. Plasma-enhanced versions of such processes may also be employed to form metal nitride layers. Illustrative examples of metal nitride layers include titanium nitride, tantalum nitride, zirconium nitride, hafnium nitride, etc.
Typically, a metal nitride layer, such as a layer of titanium nitride—in the “as formed” condition—has a relatively high intrinsic stress level, such as a relatively high compressive stress level. In general, it is desirable that the intrinsic stress level of the metal nitride layer be as low as possible so as not to transfer this intrinsic stress level in the metal nitride layer to adjacent dielectric layers, such as so-called “low-k” dielectric materials (k value less than 3), that are not as strong mechanically as the metal nitride layer. There are only a few known methods for reducing the intrinsic stress level in a metal nitride layer, such as a layer of titanium nitride. However, such methods typically result in a reduction of the density of the metal nitride layer, which may adversely impact other processing operations that are to be performed on the metal nitride layer. More specifically, reducing the density of a metal nitride layer may have the effect of reducing the etch selectivity exhibited by the metal nitride layer when it is exposed to at least some etching processes. The reduction in the density of a metal nitride layer, therefore, may require more complex and perhaps less efficient etching processes.
One technique employed in an attempt to reduce the intrinsic stress of a metal nitride layer, such as an illustrative layer of titanium nitride, involves performing a relatively high-temperature anneal process (T>750° C.) in atmospheres of hydrogen (H2), nitrogen (N2), or combinations thereof, as well as ammonium (NH3), that may reduce the intrinsic stress level in a metal nitride layer to some degree. However, such high-temperature anneals cannot be employed on integrated circuit products where copper-based metallization systems are employed.
Depending upon the allowable “thermal budget” for the particular device under construction, certain deposition techniques have been employed to form metal nitride layers with different stress conditions. For example, titanium nitride layers that are formed using a TiCl4-based CVD process tend to exhibit a tensile intrinsic stress level as originally deposited, while titanium nitride layers that are formed using a TiCl4-based PECVD process tend to exhibit an intrinsic compressive stress. The intrinsic stress levels in such CVD deposited layers of titanium nitride can be modified, to at least some degree, by modifying nitridation cycle numbers and/or processing time. Additionally, titanium nitride layers that are formed using a TiCl4-based atomic layer deposition (ALD) process tend to exhibit a tensile intrinsic stress level as originally deposited, while titanium nitride layers that are formed using a TiCl4-based PEALD process tend to exhibit an intrinsic compressive stress. From a thermal budget point of view, CVD formation of titanium nitride layers typically involves relatively high temperatures (>600° C.) although there are some CVD processes that may be performed at temperatures of down to about 350° C. (divided cycle or pulsed CVD processes). Titanium nitride layers formed using an ALD process may be formed at relatively lower temperatures (<400° C.).
Titanium nitride layers that exhibit a tensile intrinsic stress may also be formed using a metal-organic chemical vapor deposition (MOCVD) process using TDMAT (tetrakis dimethyl-amino titanium) and TEMAT (tetrakis diethyl-amino titanium) as precursors. However, the resulting titanium nitride layers with no plasma densification are not as dense as titanium nitride layers formed by other processes, and therefore tend to oxidize more easily as compared to more dense titanium nitride layers.
Despite the various techniques employed to form metal nitride layers, such as the illustrative ones briefly described above, and various attempts to reduce the intrinsic stress levels of the resulting metal nitride layers, there still is a need for an effective and efficient technique for reducing the intrinsic stress levels for metal nitride layers. Thus, the present disclosure is directed to various, more efficient methods of forming metal nitride layers on various types of semiconductor devices that may at least reduce or eliminate one or more of the problems identified above.